Organ tremulant



' H. G. BAUER ORGAN TREMULANT June 30, 1959 zvsneets-sneet 1 Filed July16, 1953 INVENTOR.

June 30, 1959 H. G. BAUER ORGAN TREMULANT 2 Sheets-Sheet 2 Filed July16, 1953 l INVENTOR BY (www s@ B@ w AL United States Patent O 'ORGANTREMULANT Howard G. Bauer, Tonawanda, N .Y., assignor to The RudolphWurlitzer Company, North Tonawanda, N.Y., a corporation of OhioApplication July 16, 1953, Serial No. 368,427 13 Claims. (Cl. 84-1.25)

This invention is concerned generally with an electronic organ, and moreparticularly with an electronic tremulant therefor.

Tremulant effects in musical instruments can be produced by variousmeans. The normal musical tremulant is a pure pitch variation such as isachieved by a violinists hand. Various mechanical devices have beenutilized heretofore to produce tremulant effects by means of pitchvariations in electronic organs. Obviously, mechanical devices inelectronic organs are undesirable as they are apt to be accompanied byelectrical noise after a certain amount of wear. All-electronictremulants in electrical organs heretofore have been devices causing avolume variation, rather than a pitch variation. The volume variationsimulates a tremulant effect, but the results are not entirelysatisfactory from a listing standpoint.

Accordingly, it is an object of this invention to provide, in anelectronic organ, an all-electronic tremulant prodncing a tremulanteffect by means of a pitch variation.

Another object of this invention is to provide, in an electronic organ,an all-electronic tremulant incorporating a pitch variation accompaniedby a relatively low volume variation.

A more specific object of this invention is to provide, in an electronicorgan, a phase shift tremulant or vibrato.

A further object of this invention is to provide, in an electronicorgan, a phase shift tremulant or vibrato by relatively emphasizingfirst one and then the other of a pair of similar signals having aconstant phase difference.

Another object of this invention is to provide, in an electronic organ,a pitch change tremulant automatically variable in pitch with themusical frequencies to produce a constant percentagewise tremulant atlow frequencies.

An ancillary object of this invention is to provide reverberation in anelectronic organ.

A further object of this invention is to provide, in an electronicorgan, a tremulant which is variable in effect and in frequency.

`Other and further objects and advantages of the present invention willbe apparent from the following description when taken in connection withthe accompanying drawings wherein:

Fig. 1 is a fragmentary perspective view of an organ embodying theprinciples of my invention;

Fig. 2 is a block wiring diagram of the organ; and

Fig. 3 is a schematic wiring diagram of the tremulant.

Referring now in greater detail to the drawings, wherein like numeralsare used to identify similar parts throughout, there is shown in Fig. 1an electronic organ 10 embodying the principles of my invention. Theorgan 10 includes a cabinet 12 having suitable keyboards 14 and a pedalclavier 16. A volume control or swell pedal 18 is provided on the organcabinet as is a loudspeaker 20 for converting electrical oscillationsinto audible organ tones.

The electrical circuit of the organ is shown in general in Fig. 2. Aplurality of bass tone generators is indicated at 22. The outputoscillations from the bass tone generators are connected in parallelthrough a wire 24 to a preamplifier 26. Similarly the output of aplurality of treble tone generators 28 is connected in parallel througha wire 30 to a preamplifier 32.. Preferably the bass and treble tonegenerators take the form of vibrating metallic reeds. As explained inHoschke No. 2,015,014, remarkably realistic organ tones can be generatedby using a vibrating reed and an associated pick-up as the plates of avariable capacitor which Varies in capacity with the spacing between thereed and pick-up and hence in accordance with the vibrations of thereeds. The reed is vibrated by means such as an air blast. In thepresent invention, all of the reeds preferably are continuously vibratedand suitable electrical connections are made t0 the various reeds andassociated pick-ups when it is desired for particular musical notes toplay.

The output of the treble preamplifier 32 is fed through a suitablecircuit 34 to a phase inverter 36. The phase inverterp36 produces twooutput signals varying substantially linearly with frequency, but alwayswith a predetermined substantially constant phase dilerence. Preferably,the two outputs differ in phase by These two outputs are fed throughwires or circuits 38 and 40 to mixers 42 and 44.

A low frequency oscillator 46 is provided and the intensity of theoutput of the oscillator as well as the frequency are adjustable bymeans of depth and speed controls 48. The output of the low frequencyoscillator 46 is suitably coupled to a phase inverter 50. The twooutputs S2 and 54 of the phase inverter 50 are utilized to control theconduction of the mixers 42 and 44 so that the mixers 42 and 44alternatively swing in accordance with the frequency of the oscillator46 from cut off condition to conducting condition, the degree ofconduction being determined by the depth and speed controls 48. Theoutputs 56 and 58 are out of phase due to the phase inverter 36, and thealternate conduction of or emphasis on the mixers 42 and 44 causes rstone and then the other to be emphasized. The outputs 56 and 58 arecombined at 60, and the alternate emphasis on rst one phase and then theother causes a phase shift tremulant or vibrato to be produced.

The combined output 60 is filtered by a low frequency filter 62 toprevent the oscillator frequency from appearing in the organ output. Itmight be well to state at this time that the frequency of the lowfrequency oscillator 46 preferably is on the order of six cycles persecond. In a specific organ constructed in accordance with theprinciples of this invention, the oscillator frequency is either 5.7c.p.s. or 6.7 c.p.s depending upon the position of the speed control 48.The output of the low frequency lilter 62 is fed through a suitablecircuit 64 to a point 66 where it is combined with the output of thebass preamplifier, the combined outputs beingap- M76 .to a phase-inverter pull output vtubes 80. 1 point thatthe phase `inverter 78could be replaced by a center-tapped transformer according to the usualpracvisvillustrated more specifically in Fig. 3. -inverter 36 isillustrated as 1/2 of a 6SN7 twin triode.

from `theplate 90 at 91 and from the cathode 92 f The-tube 864 isconventionally connected as a phase in- -verter with equal resistors-94and Arr A additional `resistor `included in the cathode circuit forbiasing `the junction of vrvalue. t As a specific example, kmicrofarad,while capacitor 104b is .0025 microfarad.

112a is .0002 microfarad and to the junction 122 between the networks108a, and 112a, 114a. of the wire or circuit 40 including a capacitor124 to the control grid 126 of the mixer l/ yof a 6SN7tube. half of.the,tube.

, halves iof .the tube are grounded through a cathode resistor 132. Thelower end of the, resistor 106!) is connected by a wire 134 to the'-juncton'136' betweenthe networks '108b,' 110b and 112b,

H4pledto a swell control 68. The swell control 68 cornprises a resistoror potentiometer actuated by the swell pedal 18 for producing an organswell.

The output of the swell control 68 is applied through a suitable wire ornetwork 70 to a gate circuit 72. This gate circuit substantiallyeliminates all signals when no notes are played, but is renderedconductive by gate switches 74 which are closed whenever one of the keysof the keyboards 14 or one of the pedals of the pedal clavier 16 isdepressed so that the musical notes may be amplified.

y The outputv from the gate circuit 72 is coupled at 78.which drives apair -of push- It is to .be understood at vthis tice for drivingpush-pull output tubes, and that the tphase inverters-36 and` 50likewise could be replaced by ,g transformers. -.output transformer 82in ;;this transformer is connected to the loudspeaker 20. A t vfeed-back.former 82 tothe gate circuit 72 for improved linearity `tofamplification-and for reducing hum.

The push-pull output tubes 80 feed an the conventional manner, and

circuit 84 is connected from the output trans- The tremulant portion ofthe organ circuit of Fig. 2 The phase a triode tube 86, specifically Theinput 34 thereto is connected to the control grid 88, while the outputis taken at 93.

96 connecting the plate the cathode to ground. 100 of relatively smallvalue is purposes and a. grid resistor-102 is connected between the gridand the resistors 96 and 100.

, The output 91 from the plate of the phase inverter 36 to a B+ line 98and 4connecting isapplied -to a pair of similar phase shifting networkscomprising series connected capacitors and resistors, the 'capacitorsbeing identified respectively by the numerals -104a and 104b, and theresistors being identified by the numerals 106a and 106b. The two phaseshifting networks, although similar in appearance, differ slightly incapacitor 104a is .00056 Each of the resistors 106a and 10611 is 62,000ohms.

The cathode output circuit 93 is connected in parallel to another pairof phase shifting networks that are similar to one another. These phaseshifting networks comprise `parallel connected resistors andy capacitorsrespectively Aidentified by the numerals 108a, -These parallel connectedresistors and capacitors are 108!) and 110a, 110b.

connected in series with grounded parallel connected :capacitors andresistors respectively identified as 112a,

112b and 114a, 11412. The cathode phase shifting networks appear similarbut different somewhat in value.

= The resistors 108e and 108b are equal, each being 360,000

ohms. The capacitor 110er is .0001 microfarad, while the capacitor 11011is .00047 microfarad. The capacitor the capacitor 112k is .00075microfarad. The resistors 114e and 114b are each 180,000 ohms.

The lower end of the resistor wires 116 and 118, these Wires 106a isconnected by having a junction at 120, 110a The junction 120 isconnected by means 44, the latter comprising The mixer 42 comprises theother The cathodes 128 and 130 of the two connectedtogether and are114b. A tap or connection 138 on the wire 134 is connected by means ofthe wire or circuit 38 including a capacitor 140 to the control grid 142of the mixer 42.

The plates 144 and 146 of the mixers 42 and 44 are respectivelyconnected through plate load resistors 148 and 150 of equal value to ajunction 152. This junction in turn is connected through a load resistor154 to a dropping resistor 156 connected to the B-lline 98. A decouplingcapacitor 158 is connected between the line 98 and ground on the highside of the resistor 156.

The low frequency oscillator 46 comprises a triode vacuum tube 160,specifically 1/2 of a 6SL7, having the cathode 162 thereof groundedthrough a self-biasing circuit comprising a resistor 164 and a capacitor166. The plate 168 is connected by a wire 170 to a resistor 172, whichis in turn connected to a resistor 174, the junction between these tworesistors being grounded through a smoothing capacitor 176. The highside of the resistor 174 is grounded through another smoothing capacitorand is also connected to a resistor 178. The high side of this latterresistor is connected by means of a wire 180 to a junction point 182which is connected through a resistor 184 to a B-lsupply line 186.

The grid 188 of the oscillator 46 is grounded through a grid resistor190 and is connected to the plate by feed-back capacitors 192, 194 and196, and a resistor 1 198 grounds the connection between the capacitors194 202 is `selectively engageable wtih any of three fixed contacts 204,2,06, or 208. The rst two-of these contacts are connected together to agrounded resistor 210 -while the third contact 208 is connected toanother grounded resistor 212. The resistors 210 and 212 are ofdifferent values, by way of illustration, the resistor 210 may be 1.2lmegohms and the resistor 212 820,000 ohms. When the movable contact 202is in engagement with either of the fixed contacts 204, 206 thefrequency of the low frequency oscillator 46 is approximately 5.7 cyclesper second, whereas when the movable contact engages the third fixedcontact 208, the oscillator frequency is approximately 6.7 c.p.s.

The plate 168 of the oscillator is connected by a wire 214 to a voltagedivider comprising resistors 216, 218, 220 and 222, the lower end of thelatter being grounded at 224. Three fixed contacts 226, 228, 230 of thevibrato depth switch are connected to the voltage divider to provideprogressively increasing oscillation voltage. The fixed switch contacts226, 228 and 230 are respectively connected between the resistors 222and 220, between the resistors 220 and 218, and between the resistors218 and 216. It will be understood that a further contact could beprovided on the high side of the resistor 216 for an even greateroscillation voltage, although the latter is not shown.

Three fixed switch contacts 232, 234 and 236 are positioned oppositelyto the vibrator speed fixed contacts 204, 206 and 208. The first ofthese, namely the contact 232, is an open contact and represents the offposition of the vibrato or tremulant. The latter two contacts, namely234 and 236, are connected in parallel. by a wire 238 to a movableswitch contact 240 selectively engageable with the three fixed contacts226, 228 and 230 of the vibrato depth control.

A movable switch contact 242 is ganged for movement with the movableswitch Contact 202 as indicated by the dashed line 244 and is cooperablewith the vibrato speed xed contacts 237., 234 and 236. When the movthefixed contacts l234, 236, the

toscillator output as determined in magnitude-bythe vibrato depthcontrol is applied by means of a vwire 246 connected to the movableswitch contact 242, a resistor 248, and a capacitor 250 to the grid 252of the phase inverter 50, the latter comprising a vacuum tube 254 whichspecifically is one half of a 6SN7. The tube 254 is connected as a phaseinverter with equal plate and cathode load resistors, identified by thenumerals 256 and 258 respectively. An additional and relatively smallcathode resistor 260 is incorporated between the cathode load resistor258 and the cathode 262, a grid resistor 264 being connected from thejunction 266 of the latter two resistors to the grid 25.2. A capacitor268 is connected from the junction between the resistor 248 andcapacitor 250 to ground at 270.

A capacitor 272 connects the plate 274 of the tube 254 to a wire 276leading to the junction 278 of a pair of resistors 280 and 282. Theresistor 280 is connected at the other end to the wire or circuit 38,while the resistor 282 is grounded at 284.

The cathode output of the phase inverter 50 is taken from the junction266 and is opposite in phase to the plate output. The cathode output isconnected through a capacitor 286 and a wire 288 to the junction point290 between a pair of resistors 292 and 294. The resistor 292 also isconnected to the grid 126, while the resistor 294 is grounded as at 296.

The outputs of the mixers 42 and 44 are combined by means of the commonload resistor 154 and the output is then transmitted by a wire 298, acapacitor 300, and a wire 302 to the grid 304 of a vacuum tube 306comprising a part of the low frequency lter 62. The cathode 308 of thetube 306 is self-biased by means of the usual grounded resistor 310 andparallel connected capacitor 312. The usual grid resistor 314 connectsthe control grid 304 to ground.

The plate 316 is connected through a plate load resistor 318 to thejunction 182 for supplying B-lpotential to the tube.

The low frequency filter 62 also includes a network connected to theswell control by means of the wire or line 64. This network includes aresistor 317 connected to the swell control and also to a capacitor 319,the latter being connected to a junction point 320. The junction point320 is grounded through a resistor 322, and is also connected to aparallel connected resistor 324 and capacitor 325. This resistor andcapacitor are connected in turn to a capacitor 326 which is connected toa capacitor 328 through a junction point 330. The junction point 330 isdirectly connected by means of a wire 332 to the plate 316 of the vacuumtube 306 for connecting the output of this tube to the network. Thecapacitor 328 is connected through resistors 332 and 334 to the grid 304of the tube 306, the junction 336 between the resistors 332 and 334being grounded through a capacitor 338.

Operation parts, but rather with the treble circuit and the tremulant orvibrato therein.

The oscillations generated by the treble tone generators are amplifiedby the'preampliiier 32 and are applied to the phase inverter 36.Referring now to Fig. 3, thel outputs taken from the output junctionsV1207,and 138 vary substantially linearly with the frequency of theinput oscillations, but maintain a constantphase angle relation betweenone another. Mathematical relations can be and have been worked outexplaining the phase shifting. However, the mathematical relationshipsdo not clarify the end result anymore than the simple explanationfollowing immediately hereinafter.

Referring first to the circuits having the identifying numerals endingwith the suliix a, it will be seen that at low frequencies the impedanceof capacitor 104a is very high and practically the entire transmissionfrom the phase inverter tube 86 takes place through the resistance 108a,the capacitor l10n also having practically infinite impedance. At higherfrequencies the capacitor 104a passes the oscillations more freely thanthe resistance 108a, and 180 of phase shift takes place in the voltagebetween the output terminals. On a further increase in frequency theimpedance of capacitor 104:1 becomes low relative to that of theresistor 106g, and the latter controls transmission through this branch.At still higher frequencies the impedance of capacitor 110:1 graduallyreduces and this capacitor finally passes oscillations more freely thanresistor 108s, thereby producing a further phase shift. Thus as thefrequency varies from the low end of the range to the high end, a

complete 360 phase shift takes place in the voltage at the outputterminals.

The operation of the phase shifting network similar to that justdescribed and identied by numerals ending with the suffix b is similarto that of the network just described except that diiferent values arechosen for the circuit elements as heretofore described and set forth byway of illustrative example so that the outputs of the phase shiftingnetworks as applied to the wires of the circuits 38 and 40 are at alltimes substantially 90 apart. The outputs, of course, are identicalexcept for this phase difference.

The two signals 90,out of phase are combined in the common output of themixers 42 and 44. The 90 phase difference causes a slight reverberationin the tonal output of the organ, thus giving the effect of a large pipeorgan installation.

The output of the low frequency oscillator 46 is converted into twosignals 180 apart by the phase inverter 50, and these signals areapplied to the grids of the mixers 42 and 44 along with the musicaloscillations which are 90 apart. The biasing of the mixers and Vthemagnitude of the amplified oscillations of the low frequency oscillatorare such that each tube 42, 44 is first conducting with relatively highamplification, and then is cut down to relatively low amplification. Thetubes operate 180 apart so that first the output of one of the tubes 42,44 is emphasized, and then the other. The result is that the combinedvoutput of the mixers 42,

' 44 shifts back and forth between the 90 out of phase musical signalsto effect a phase shift vibrato or tremulant. The degree of phase shiftis determined by the position of the movable switch contact 240 of thedepth and speed controls. When the greatest depth of vibrato is appliedeach of the tubes 42, 44 is alternately highly conductive andsubstantially cut off. This effects a maximum phase swing and asubstantial tremulant or vibrato. When the vibrato is applied withlesser depth, the relative conductivities of the two tubes 42, 44 arenot changed to such a great extent. Accordingly, the combined outputdoes not swing as far, and the vibrato or tremulant is lessened.

The components in the phase shifting circuits are so chosen as tomaintain a substantially 90 phase shift between 500 cycles and 15,000cycles. Above and below these values the phase shift becomesprogressively less as the frequency moves away from these values. When vthe two signals 90 out of phase are controlled or modu- `lated in themixers by the output of the low frequency oscillator, the modulation isuniform over the band between 500 cycles and 15,000 cycles. Thepercentage of the percentage of modulation) must remain substantiallyconstant to maintain a uniform tremulant effect.

Accordingly, asv noted above,. the phase'shifting circuit components arechosen so that the phaseshift, and consequently the degree of modulationor vphase swing, progressively decreases below 500 cycles. As aresultthe `percentage of modulation or phase swing remains *at` a constantpercentage of the musical tone frequency below approximately 500 cycles.

It will be understood that the maximum .phase swing is somewhat lessthan the 90 between the two input signals to the mixer. By way ofexample, the maximum `phase swing for optimum results is approximatelyone radian, or about 57.

The combined output of the mixer is applied to the .low frequency filter62 comprising the tube306 and kthe circuits associated therewith. Thisfilter cutsV off sharply below 130 cycles per second to keep the lowfrequency oscillator signal from appearing inthe output of the organ.generated by the bass tone generators. .The output of the low frequencyfilter is applied to the swell control along with the base tonegenerators, and the bass and treble signals thereafter are handledtogether.

The inherent characteristics of the modulator or mixer tube 42, 44 aresuch that some amplitude variation is introduced along with the pitchVariation. The amplitude modulation is relatively small, being on theorder of and adds to the pleasing effects of the phase shift vibrato onthe human ear. I

The specific structure herein shown and described is by way of exampleonly. Various modifications can be made in the structure and are to beconsidered as forming a part of my invention insofar as they fall withinthe spirit and scope of the appended claims.

I claim:

l. An electronic organ tremulant comprising a tone generator, meansconnected to said tone generator for splitting the tones generatedthereby into a plurality of signals differing in phase by asubstantially fixed predetermined degree substantially less than 180,and electronic means connected to said splitting means for combining theplurality of signals produced and including electronic means forrelatively emphasizing one phase and then the other at a tremulantfrequency to produce a tremulant effect.

2. An electronic organ tremulant comprising a tone generator, meansconnected to said tone generator for splitting the tones generatedthereby into a plurality of like signals differing substantially 90 inphase, and electronic means connected to said splitting means forcombining the plurality of signals produced and including electronicmeans for relatively emphasizing one phase and then the other at atremulant rate to produce a tremulant effect.

3. An electronic organ tremulant comprising a tone generator, meansconnected to said tone generator for splitting the tones generatedthereby into a plurality of signals varying in phase with the frequencyof the tones generated but having a substantially constant phasedifference, electronic means connected to said splitting means forcombining the plurality of signals produced and including electronicmeans for relatively emphasizing one phase and then another in a cyclicmanner at a tremulant rate to produce a tremulant effect.

4. An electronic musical instrument tremulant comprising a generator ofelectrical oscillations corresponding to a musical tone, an electronicamplifying device having anode, cathode, and control elementconnections, said oscillation generator being connected to said controlelement, a pair of anode circuit phase-shifting networks rconnected incommon at one end to said anode connection, a pair of cathodephase-shifting networks connected in parallel to said kcathodeconnection, `meansrminter- All musical tones under 130 c.p.s. are

network,` a pairof electronicY amplifying devices having common anodecircuits and common cathode circuits, and having independent controlelements, means connecting one of said interconnections to one of` saidlastmentioned control elements and the other of said interconnections tothe otherof `saidflast-mentioned control elements, an oscillationVgenerator providing electrical oscillations atV a Vtremulant frequency,means applying the output of said tremulant` oscillation generator inopposite phase to said last-mentioned control elements wherebyalternately to emphasize the musical tone oscillations applied thereto,kand means connected to said common anode circuit: for converting thelelectrical oscillations in r.said common anode Acircuit into audiblemusical tones having a tremulant impressed` thereon.

5. An electronic musicalinstrument tremulant as set forth in claim 4wherein each anode phase-shifting net- `work comprises aseries-connected resistance element and capacitance element,; and`wherein each.` cathode phaseshifting network comprises aparallel-connected resistance element and capacitance element. i

6. An electronic musical instrument tremulant as set vforth inl claim 5wherein anelement in one anode phase- `work comprises a second parallelconnected resistance element and capacitance element in series with thefirstmentioned parallel connected resistance element and capacitanceelement and connected thereto at a junction.

8. An electronic musical instrument tremulant as set forth in claim 7wherein each anode phase-shifting network is connected to the junctionof the corresponding cathode phase-shifting network.

9. An electronic musical instrument tremulant as set forth in claim 7wherein each cathode control element is connected to ground through apair of series connected resistors connected together at a junction, thejunction of each pair of resistors being connected to the junction ofthe corresponding cathode phase-shifting network.

l0. An electronic organ tremulant comprising a tone generator, and atremulant producing device acting on the tones produced by said tonegenerator, said device comprising a vacuum tube having a cathode, aplate, and a control grid, means connecting the tone generator to saidcontrol grid, a pair of resistance-capacitance phase shifting networkseach having components connected to said plate and having componentsconnected to said cathode, the plate components of the two networkshaving similar elements, but `of different values, and the cathodecomponents of the two networks also having similar components, but ofdifferent values, electronic mixing means, means differentlyy connectingthe two phase shitting networks to said mixing means, ysaid phaseshifting networks providing signals `to said mixing means, which areoutof phase relative toone another, and means connected to saidmixingrmeans for successively relatively emphasizing the signals fromone phase shifting network and relatively minimizing the signals fromthe other phase shifting network.

ll. An electronicworgan, `tremulant asvset forth in claim luwhereinujtheplate-connected components* of each phased-shifting networkcomprisewseries connected 9 resistance and capacitance elements and thecathodeconnected components of each network comprise parallel connectedresistance and capacitance elements.

12. An electronic organ tremulant as set forth in claim 11 wherein thecathode-connected components of each network comprise a rst combinationof a parallel connected resistance element and capacitance element, anda second combination a parallel connected resistance element andcapacitance element, said first and second combinations being connectedat a junction and serially connected between said cathode and ground.

13. An electronic organ tremulant as set forth in claim 12 wherein theplate-connected components of References Cited inthe tile of this patentUNITED STATES PATENTS 2,048,900 Usselman July 28, 1936 2,148,478 KockFeb. 28, 1939 2,233,948 Kock Mar. 4, 1941 2,300,999 Williams Nov. 3,1942 2,382,413 Hanert Aug. 14, 1945 2,534,342 Daniel Dec. 19, 19502,583,566 Hanert Jan. 29, 1952

